This invention relates to a control valve arrangement for an articulated vehicle having separate parking brake systems on the powered, or tractor, portion thereof and on the nonpowered, or trailer, portion thereof.
Existing tractor-trailer articulated vehicles are commonly supplied with separate parking brake systems on the tractor and trailer portions thereof. Commonly, these parking brakes are of the conventional spring applied, fluid pressure released type well known to those skilled in the art. These braking systems require communication of fluid pressure to the parking brakes to release the parking brakes, and permit application of the parking brakes by venting this hold-off pressure when the vehicle is parked or under emergency conditions. As can be appreciated by those skilled in the art, existing parking brake control systems are relatively complicated, and require at least three manually operated valves and an additional control valve in order to completely control communication to the parking brakes. Not only is this system unduly complicated, but the control valves themselves are relatively expensive, so that elimination of one or more of these valves is obviously desirable. Furthermore, these prior art systems may actuate the tractor brakes alone by operation of a single one of these valves. This is undesirable, since in the usual situation, both the tractor and trailer parking brakes should be applied simultaneously, although there will be instances when the trailer parking brakes must be later released after a parking brake application while the tractor parking brakes are maintained in their applied condition.